Locking devices of this type are already known which consist of a frame made up of two long members connected together by two end cross members and capable of being fastened to the floor of the space in the vehicle intended to take the cargo instead of one or more running rollers or balls fitted to the floor for handling the containers or pallets. A first and a second latch, hinged to each other at one of their ends by a common transverse pivot pin, are mounted in this frame. The first of the said latches has as its other end a transverse hinge pin fitted in a fixed position between the said long members. The second of the said latches has at its other end a transverse hinge pin guided in translation in longitudinal slideways in the long members. Means are provided for changing the said latches from a cargo unlocking position in which the said latches are retracted down into the said frame to a cargo locking position in which the latches project up above the frame. Finally means are provided for blocking the latches in this cargo locking position.
According to a known embodiment of these locking devices, the latches are acted on and held in the cargo unlocking position by a spring. The blocking means provided on the locking device then hold the latches, against the action of this spring, in the cargo locking position. In order to change the latches from the cargo locking to the unlocking position, all that is needed is to step on a lever acting on the said blocking means, so that the released latches, under the action of the said spring, automatically go over to the cargo unlocking position. In order to bring the latches from the unlocking position to the cargo locking position it is necessary, on the other hand, to exert a pull, by hand, on a ring provided on the pin shared by the two latches and pull the latter against the action of the spring as far as the cargo locking position in which the latches are held by the above-mentioned blocking means.
According to another embodiment of these known locking devices in which the latches are also acted on and held in the cargo unlocking position by springs and are held in the cargo locking position, against the action of the said springs, by blocking means, the lever provided to release the latches in the cargo locking position makes it possible, by means of a gear transmission system, to also, on stepping on this lever, bring the latches, against the action of the said springs, from the cargo unlocking to the cargo locking position. However, this foot operation of the lever to change the latches over from the unlocking to the cargo locking position implies a relatively large steady force and the gear transmission system between the said lever and the latches makes the locking device construction significantly more complicated.